This
article is about Late Roman army commands, under the
understanding that the Roman army was not a clear-cut
affair. First of all, we have to distinguish between
ranks, titles and grades. This can be confusing, because
sometimes titles evolved into ranks, and some ranks are
without an earlier equivalent.

THE
CHANGES OF DIOCLETIAN

When
we discuss the hierarchy of the Late Roman army, it's
important to first get an idea of what we are discussing.
Contrary to popular view, the Roman army was not an army
comparable to modern armies. Changes were slow to be
implemented, uniformity as we know it most probably did
not exist, and standards like unit strength or uniformity
in command structure was not the same all over the empire.
The same goes for the 'new model army' that was developed
by Diocletian and his successors (especially Constantine).

From
the literary evidence (legislation, papyri,
hagiographical and historical literature from historians
such as Ammianus Marcellinus, bureaucratic
documents such as the Notitia Dignitatum,
tactical treatises such as the Strategikon or
the inscriptions found throughout the empire, mostly on
funerary monuments) we gather that Diocletian did not
alter the structure of the 'old-style' units. These 'old-style'
units such as legiones (regardless of these being
later classed as palatinae, comitatenses or
limitanei), cohortes and alae
retained the same traditional internal structure and
ranking system which they had during the Principate, and
which remained the same until the 7th c. Their
officers continued to be called tribunes, centurions and
decurions. At the same time, 'new-style' units were
created with apparently a different hierarchy of ranks
and posts, limited to newly created units of the comitatenses,
namely scholae, vexillationes, auxilia palatini
and some cunei.

RANKS,
POSTS, TITLES AND GRADES

Ranks
are the true steps on the ladder of command. Well
try to filter out these true ranks, even
though this can be very difficult.
Although Maurikios only mentions the tribunus in
his Strategikon, this does not mean that he abolished
these titles in a reform (or reflecting a 6th-c.
evolution), since many of them are mentioned in other
sources up to the 10th c. That most are
missing from the Strategikon may be due to the fact that
everything not related to drill was omitted. Maurikios
Greek ranks may just be his own descriptions
for operational roles, as they are descriptions of the
command: ilarch, merarch (commander of a
meros or division), hekatontarch (commander
of a hundred), dekarch (commander of
ten), pentarch (commander of
five) or tetrarch (commander of
four). Some of them are genre-terms or even coined
by himself as a cover-all for the varying titles and
ranks in use for some posts (such as second-in-command
possibly being the primicerius, vicarius or
domesticus). But since we know that the 'old-style'
units still existed next to the 'new-style' units in
Maurikios' days, we can posssibly conclude from these
generic names that the officers and nco's of the Roman
army, although bearing different names, still existed. It
means that both type of units looked similar and could be
used next to each other at will. For example, a
centenarius was the same function as the centurion, and
both were still commanding a hundred men by the late 5th
century.
Latin remained the language of the army until the 630s
and Greek words and translations (such as hekantontarch
instead of centurio) also know from earlier
sources such as Arrian, were probably not the
nomenclature used in the real-world Roman
army.

Posts
are temporary commands or duties, which could be held by
men of different ranks, the seniority depending on the
responsibilities and time for which the command could be
held. Examples of such posts are the vicarius (in
fact an acting tribune) and the domesticus
(acting regimental chief-of-staff).

Titles
are often confused with ranks. This is not surprising
given the limited knowledge that we have of the Late
Roman army and its structure. Add to that the fact that
titles could be similar for civilian and military (such
as the Magister), the inconsistency with which
titles were used and the evolving meaning. In principle
though, titles could be held by men of different ranks,
and there seems to have been a rank-like hierarchy
involved (such as Comites de facto outranking Duces).

Grades
have to do with pay or denoting seniority and privileges,
and several grades can be included in one rank. Another
difference in pay grade was determined by the army class
of a particular unit. Soldiers were paid more when they
served in units that belonged to the comitatenses
instead of the limitanei, and even more in the auxilia,
scholae and palatini.

The
only fourth-century list of these Late Roman regimental
grades or indeed a pay-scale is from
Hieronymus writing ca. 386-7 (Jerome, Contra Johannem
Hierosolymilanum episcopum 19 (PL23, 370);

tiro

eques or pedes

semissalis

circitor

biarchus

centenarius

ducenarius

senator

primicerius

tribunus

The
only connection to the actual amount of money paid to (some
of) these ranks and grades comes from an edict of April
13, 534 from Justinian issued to Belisarius in North
Africa (Codex Justinianus I.27.2:19-36, which
stipulates the salaries of military clerks in the five
newly re-created African ducates after Belisarius
victory over the Vandals.

One
annona equalled 5 nomismata or solidi (one year of ration's
worth), and one capitus equalled 4 nomismata or solidi (one
year of fodder for the horse):

Most
of these confirm the list of Jerome (the recruits and
rankers are left out since there were no clerks of that
rank), and from the amounts paid to the numerarius
and the assessor we can concluded that these
compare to the senator and tribunus
respectively. Similarly, the rankers perhaps received one
annona, one capitus if cavalry, equalling nine nomismata,
and the recruit perhaps a half annona, one capitus if
cavalry, equalling six-and-a-half nomismata.
We know from a law of Julian that a domesticus
reived six capitus and therefore probably eight or even
ten annonae or more (their children received already four
annonae acccording to a law of Valentinian I). According
to the Justinian Codex (I.27.2:20-21), a dux
eceived a salary of 1.582 nomismata but they
regularly pocketed annonae from the lower ranks as an
extra source of income.

HIGH
COMMAND

The magister
was the replacement of the praefectus praetorium
since the time of Constantine. The magister officiorum,
a civilian official, commanded the scholae, but
Constantine meant the bulk of the armed forces to be
commanded equally by the magister peditum (general
of the infantry) and the magister equitum (general
of the cavalry). However, this system soon evolved. More
magistri were appointed, such as the magister
praesentalis or the magister in praesenti (magister
commanding the forces in the presence of the Emperor), or
regional commanders such as the magister militum per
Gallias, per Orientem, per Thracias, etc.
Its unclear if magister was originally a
title or a rank, although it may have evolved into a rank.
The substructure of the magistri is not known, also
because the (apparent) titles were inconsistently used.
Even in law codes, a single magister is addressed
as magister equitum et peditum and comes etmagister militum. Other such forms include the
more known magister utrisque militae or the widely
used simple magister militum. The men in these
posts (or ranks) were addressed as Perfectissimi,
Clarissimi, Illustrissimi, Magnifici and Gloriosi,
and only outranked by the city prefects or the praetorian
prefects.
In the East, the command structure remained decentralised,
the praetorian prefects always remained more powerful
than the magistri, and the Emperor always retained
overall command. However, in the West the system became
largely centralised  in the late 4th
century, the magister peditum praesentalis
obtained command over all the troops, and men like
Arbogast, Stilicho and Aetius held almost supreme power.
After 416, the magister peditum praesentalis held
the title patricius. When the actual power of the
Emperors began to decrease, this Patrician (notably men
like Aetius and Ricimer) went on to become the de facto
regent of the Western Empire.

GENERALS

When
Constantine segregated the civil and military functions,
the military commanders ceased to be civil governors (although
in some cases there were exceptions). Provinces were
henceforth commanded by praeses without military
functions, while the troops were commanded by duces.
There seems to have been no sharp distinction between comites
and duces.

The comes
(title) was originally a title (lit. meaning
companion) for members of the entourage of
the Emperor, not a rank. Later the title became known for
several functions, both military as well as civilian.
These functions were formalised by Constantine, by
creating titles such as the comes sacrarum
largitionum (finance minister), the comes
domesticorum (commander of the protectoresdomestici).The
military version of the title was the comes rei
militaris, a vague title without a description of
rank or importance, which could describe commands varying
from minor frontiers to overall army command of a magister
militum.
The comitatenses or field armies of a certain region
always commanded by a comes (such as the comes
Britanniarum) and was therefore possibly higher in
status than a dux. A comes, however could,
like a dux, also command a regional army group,
indeed like the comes Litoris saxonicum per Britannias
(count of the Saxon shore) or even frontier sections (law
codes prove the existence of a comes limitis). Comites
could also command vexillationes of the mobile field army
in the field.

The dux
(rank) was originally a title (lit. meaning
leader) of an officer acting in a temporary
capacity above his rank, commanding a collection of
troops in transit or in temporary command of a single
unit. From the third century, a dux became a
regular officer. After Constantine, the dux
commanded the provincial troops (the comitatenses
and palatini falling under the command of the magistri
or comites). Such a command could encompass a (part
of a) province (styled after the name of that province,
such as the dux Aegypti) or even several provinces
(such as the dux Britanniarum (duke of the
Britains), who commanded the regions straddled by Hadrian's
Wall). Another name could be dux limitis, but
these names were not standardised.
The dux ranked directly below the magister
militum (but could appeal to the Emperor) and was
responsible for the military protection of his own sector,
including the military infrastructure, the collection and
distribution of provisions and the military legal system.
Valentinian I raised the duces from equestrian to
senatorial status, which also reflects the
inflation of some military commands, which
saw the replacement of several duces with comites
during the fifth century. A dux received a
salary of 1.582 nomismata (equalling 190 annonae
and 158 capitus).

OFFICERS

The tribunus (rank)
was the commanding officer of a new-style unit, which
could be a regiment of auxilia palatina or a numerus
or anything in between. Tribuni of the scholae
were commanded by the magister officiorum, but tribuni
also commanded cavalry vexillationes, new-style auxilia
regiments as well as the new-style legions of the field
army, but also the old-style cohorts of the limitanei.
By the mid-fifth century a tribunus might also be
styled a comes, under the debasement of Roman
military titles. By the sixth century a papyrus describes
an old-style cohort commanded by a tribunus, eight
senior officers including the adiutor (regimental
clerk), the primicerius, six ordinarii and
six others, probably the centuriones.
A so-called tribunus vacans was an officer
temporarily without unit serving as a staff officer.
These tribuni vacantes could also serve on special
duties  when Ammianus was on a misssion from
Ursicinus to relieve the magister peditum Silvanus
of his command (read arrest him), he and his
nine fellow domestici were accompanied by several tribuni
vacantes. And in Egypt, a tribunus civitatis
might combine military and civilian duties, acting like a
governor. Tribuni could also be in charge of
barbarian groups, as the example of the Tribunus
gentis Marcomannorum shows. We know of one Agilo who
was a tribunus stabuli in 357. These men (later
comes stabuli) were responsible for gathering
levies of horses for the army. A tribunus
received 40 nomismata, 7.5 or probably eight
annonae (plus four capitus if cavalry).

The praefectus
(rank) was the officer in command of old-style legions (praefectus
legionis) and of old-style alae (praefectus alae),
although these were only to be found in the West, notably
on the Danube and in Britain. Praefecti could also
command several units together, as seen with the praefectus
legionis quartaedecimae geminae militum liburnariorum
cohortis quintae partis superior, Carnunto, who
commanded the fourteenth legion as well as a part of the
Danube fleet plus the fifth cohort, from his command post
at Carnuntum.

The praepositus
(post) was originally a title for any officer in
temporary command of a unit, usually a vexillation on the
way to or from a battle, later a classic numerus.
This title could be held by officers of several ranks;
prefects, tribunes or legionary centurions. In the Later
Roman army, the praepositus was (like the comes) a
name for a post, tribunes and prefects being addressed as
praepositus or officer-commanding.
Most of all we come across the praepositus as
commander of old-style units, notably in the African
provinces. Praepositi could command scholae
units as well as old-style legions (praepositus
legionis), old-style cohorts (praepositus cohortis),
but there are also commands of less known units (praepositus
militum, praepositus equitum and praepositus
auxilia). Of course here, too, titles were used
inconsistently, as is proven by the case of a prefect of
an old-style ala (one Flavius Abinnaeus at
Dionysias), who was also addressed with the title praepositus,
and even as praefectus castrorum. In Africa, the
limes was divided into sections, each commanded by a praepositus
limitis subordinate to the dux. A praepositus
could also command groups of laeti (praepositus
laetorum), which were groups of barbarians who had
been defeated in a campaign and settled throughout the
empire under Roman supervision.

The protector
(title) was originally a member of the select corps that
Gallienus created as a group of loyal men around him.
This group changed into a kind of school for officers,
making men who were promoted from the ranks to become a protector
before they were posted to their new ranks and duties.
Some of these protectores were posted to the staff
of field commanders (deputati) to gain experience,
and performed a great number of duties. They could be
sent to round up recruits and vagrants, or act as border
guards controlling exported goods. Their more military
duties could include the arrest of important persons, as
related by Ammianus Marcellinus, who himself was a member
of the ten protectores domestici in the staff of
the general Ursicinus. This group was named domestici
(men serving in the entourage of the Emperor, although
also dispersed over the lower army staffs) to distinguish
them from ordinary protectores, who succeeded to a
command of a unit after serving for a number of years as protector.
Other military tasks included special misssions, such as
preparing temporary forts on campaign, or the arrest of
officers.
When a soldier reached this stage of cadet officer, it
finally meant a break from his original unit, because
only the Emperor could decide to transfer men from one
unit to another. Promotion was therefore very slow and it
is not surprising that higher officers used their
influence to get instant commissions for their sons.
Bribery was rife in the Roman army, but men appointed
thus instead of rising through the ranks had to pay
certain fees and charges. When during the fifth century
the flexibility of the promotion system decreased, the domestici
and protectores became a static body.

NCOs

The primicerius
(rank) was the senior NCO (both in old-style as well in
new-style units) whose name came first on the regimental
muster-roll (matrix). A primicerius can be
compared to a regimental lieutenant-commander, replacing
an absent tribunus in the guise of the vicarius
or as the tribunes domesticus. Primicerii
played an important role in the day-to-day administrative
affairs. In the scholae they ranked as clarissimi,
equal in standing to the tribunus, the next step
in promotion. In unofficial sources the term becomes a
generic description of any senior regimental officer. A primicerius
received five annonae (plus two capitus if cavalry).

The vicarius
(post) was the highest non-commissioned officer and could
assume command in absence of a tribunus. He
was not a strict rank but an acting-tribune,
sometimes even from another unit. The formulaic coupling
vicarius vel tribunus from a number of
sources signified the title of commanding
officer or officer in charge regardless
of his actual rank. When an infantry regiment was split
into two equal parts, the tribunus commanded the
first and the vicarius the second. Maurikios
mentioned the ilarch (or the senior hekatontarch)
for the case of a cavalry regiment, but see above.
Vegetius mentioned a tribunis minor, which might
signify a change in promotion procedured, or he might
have had the vicarius in mind.

The domesticus
(post) was a regimental chief-of-staff or adjutant. The
term was also used in military and civilian life for a
great number of assisting officers and officials with
varying ranks. See also protector. Not to be
confused with the select corps of domestici who
accompanied the Emperor.

The campidoctor
(rank) used to be as the regimental drill master or chief
training-officer of the Principate (before
that and afterwards, a training officer was known as the exercicator
or doctor armorum / armidoctor). Although
it is still unclear if the roles and seniority of the campidoctor
in old-style and new-style units were comparable, both
Vegetius and Maurikios use the term for a regimental
drill master. However, the campidoctor developed
into one of the most important NCOs, exclusive to
the infantry. Ranking third behind the tribunus
and the primicerius, and on occasion the campidoctor
could (like the vicarius) take command of (part of)
an infantry unit.
According to Maurikios, the campidoctores
accompanied the tribunus before the engagement,
before taking their place besides the standard in battle.
Vegetius as well as Ammianus associated the campidoctores
with the classical antesignani (in a non-technical
classicising manner), signifying that they fought in the
front rank.

The senator
(rank) served in several troop types including the scholae,
but otherwise nothing is known about this rank. A senator
received probably four annonae (plus two capitus if
cavalry).

The ducenarius
(rank) originally was a class of minor judges who sat in
minor cases (Suetonius, In Augustum, cap. XXXII). There
was also a civilian ­procuratorducenarius. Not
much is known of the Late Roman ducenarius,
although he may have commanded two hundred men, which
would be logical if the new-style campidoctor commanded
part of a unit. However, this may be due to a
misunderstanding of Vegetius, who mentioned this rank as
a rank between the centurion and the primus
pilus of his theoretical Legio Antiqua.
Vegetius was in all probability wrongly equating
ducenti into ducentenarius. A
classic example of a ducentenarios however is
not known from the military, but from horse-racing, as a
horse with two hundred victories (Diocles). As a result
we cannot be sure if Vegetius, as he often did, made
something up or mentioned the actual number of men under
the command of a ducenarius. The word
ducentenarius as a commander of two hundred
men is not known before Bede (8th c.). A ducenarius
received three-and-a-half annonae (plus one-and-a-half
capitus if cavalry).

The centenarius(rank) likewise seems clear-cut as a commander of a
hundred men, but although Vegetius compares them to centuriones
(maybe just by etymology), its by no means sure
that the name refers to the number under his command.
Lucius Artorius Castus was a procurator centenarius
of Liburnia. The second-century title procurator
centenarius may have referred to his salary, and the
Late Roman centenarius portus (a unique command
mentioned for the city of Rome) seems too important to be
just a centurion. Maybe its not
surprising that, like the ducenarius, the centenarius
was also originally a legal function. A centenarius
received two-and-a-half annonae (plus one capitus if
cavalry).

The ordinarius
(rank) seems to have been the same as the centurion of
the old-style regiments, commanding eighty men according
to a papyrus describing a sixth-century cohort. Odd
enough, the ordinarius, although widely attested, does
not appear in either Jerome's or Justinian's list, so
perhaps

The biarchus
(rank) seems to have been a junior officer comparable to
the decuriones which continued to exist in old-style
units and who commanded an eight-man strong contubernium.
The word biarchus literally means in
charge of the food supply, or mess-leader
or caput contubernium, which may indeed point to
his practical role in commanding a contubernium.
Vegetius refers to this rank as the decanus,
comparable to Maurikios dekarch, which
means set over ten or commander of
ten. Both may well have been purely theoretical
though (comparable to a centurio commanding 80 men
instead of a 100), instead of signifying a real change of
the contubernium from eight to ten men.
The first example known of a biarchus is from a
tombstone from Concordia of a biarchus draconarius.
This Flavius Iovianus, serving in a late fourth-century
vexillation of the Octavodalmatae, was therefore probably
the file-leader as well as the draconarius. The optio
draconarius may refer to a similar combination. A biarchus
received two annonae (plus one capitus if cavalry).

The circitor
(grade) was the lowest NCO grade. According to Vegetius,
the circitor was once a post of the inspector of
the sentries, but evolved into a rank of which we know
little to nothing. A law of Constantine stipulated that
sons of cavalrymen could, provided he brought two horses
or a horse and a slave, start immediately as circitor.
A circitor received two annonae (plus one
capitus if cavalry).

ENLISTED
MEN

The semissalis
(grade) may have been a senior soldier with higher pay,
receiving one and a half annonae (plus one capitus if
cavalry).

The pedes
and the eques (rank) were the
common privates of the infantry and the cavalry. A pedes
may have received one annona, and an eques may
have received one annona plus one capitus.

The tiro
or recruit was the lowest rank in the army, which a man
held from joining during his training period. During this
time he did not receive full pay and allowances. An
advice to Valens and Valentinian entailed keeping groups
of between fifty and a hundred tirones attached
to each unit, admitting them upon vacancies. A tiro
may have received a half annona (plus one capitus if
cavalry).

Rance, Philip (2007):
Campidoctores Vicarii vel Tribuni: The
Senior Regimental Officers of the Late Roman Army
and the Rise of the Campidoctor, in: Ariel
S. Lewin and Pietra Pellegrini (eds.) (2007): The
Late Roman Army in the Near East from Diocletian
to the Arab Conquest, pp. 395-409.